Liquid discharge head

ABSTRACT

There is provided a liquid discharge apparatus which includes a channel substrate having a nozzle, a pressure chamber which communicates with the nozzle, an actuator which covers the pressure chamber, and a contact point that is electrically connected to the actuator, and a circuit board which has wires that are to be electrically connected to contact points, and which is adhered to the channel substrate. The channel substrate includes an adhesive wall which is provided with contact points, and which has a surface to which an adhering portion of the circuit board to be adhered to the channel substrate, is adhered, and further includes a wall portion which is provided with a cavity on a side of the adhesive wall, opposite to the surface, and which demarcates the cavity on a side opposite to the surface, of the adhesive wall, and the adhering portion is facing the cavity and the wall portion.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2017-066805, filed on Mar. 30, 2017, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND Field of the Invention

The present teaching relates to a liquid discharge head which includes achannel substrate having contact points, and a circuit board havingwires that are to be electrically connected to the contact points.

Description of the Related Art

In liquid discharge heads, the circuit board is adhered at a positionfacing a cavity formed in the channel substrate. For instance, in aknown liquid discharge head, a circulation channel (cavity) is formed inthe channel forming substrate (channel substrate), and the circuit boardis adhered on a wall at a position facing the circulation channel. Thewall is provided with a contact point of the channel forming substrate.

SUMMARY

In the abovementioned liquid discharge head, the whole of a portion, ofthe circuit board, that is to be adhered to the channel substrate isfacing the cavity. The portion, of the circuit board, that is to beadhered to the channel substrate is referred to an adhering portion ofthe circuit board. Consequently, at the time of adhering the circuitboard to the channel substrate, the wall of the channel substrate isdeformed due to a load exerted to the adhering portion. In some cases,the wall of the channel substrate may be damaged.

An object of the present teaching is to provide a liquid discharge headwhich is capable of suppressing a problem of the wall of the channelsubstrate getting deformed at the time of adhering the circuit board andthe channel substrate.

According to an aspect of the present teaching, there is provided aliquid discharge head including: a channel substrate including a nozzle,a pressure chamber communicating with the nozzle, an actuator coveringthe pressure chamber, and a contact point electrically connected to theactuator; and circuit board including a wire electrically connected tothe contact point, the circuit board being adhered to the channelsubstrate at an adhering portion of the circuit board. The channelsubstrate includes: an adhering wall having a surface on which thecontact point is located, and to which the adhering portion of thecircuit board is adhered, and a wall defining a hollow space located ona side opposite to the surface of the adhesive wall, and the adheringportion of the circuit board faces the hollow space and the wallportion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a printer 100 equipped with a head 1according to a first embodiment;

FIG. 2 is a plan view of the head 1 (a reservoir member 11 a, aprotective member 15, and a protective film 12 i are omitted);

FIG. 3 is a cross-sectional view along a line in FIG. 2;

FIG. 4 is a diagram showing an area IV in FIG. 3;

FIG. 5 is a diagram showing an area V in FIG. 3;

FIG. 6 is a diagram showing an area VI in FIG. 2;

FIG. 7 is a cross-sectional view along a line VII-VII in FIG. 6;

FIG. 8 is a diagram corresponding to FIG. 5, of a head 201 according toa second embodiment;

FIG. 9 is a diagram corresponding to FIG. 5, of a head 301 according toa third embodiment;

FIG. 10 is a diagram corresponding to FIG. 5, of a head 401 according toa fourth embodiment;

FIG. 11 is a plan view corresponding to FIG. 2, of a head 501 accordingto a fifth embodiment; and

FIG. 12 is a plan view corresponding to FIG. 2, of a head 601 accordingto a sixth embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS First Embodiment

An overall configuration of a printer 100 equipped with a head unit 1 xincluding a head 1 according to a first embodiment of the presentteaching will be described below with reference to FIG. 1. The head 1corresponds to the liquid discharge head of the present teaching. Theprinter 100 includes a platen 3, a conveyance mechanism 4, and acontroller 5, and the head unit 1 x.

The head unit 1 x is of a line type (in other words, a type in which anink is jetted on to a paper 9 in a state of a position being fixed), andis long in a direction orthogonal to a conveyance direction. The headunit 1 x includes four heads 1 arranged in a zigzag form along thedirection orthogonal to the conveyance direction. The four heads 1 havethe same structure mutually. Each head 1 discharges an ink from aplurality of nozzles 11 n (refer to FIG. 2 and FIG. 3).

The platen 3 is arranged above the head unit 1 x. An ink is dischargedfrom each head 1 on to the paper 9 supported by the platen 3.

The conveyance mechanism 4 includes two pairs of rollers 4 a arranged tobe sandwiching the platen 3 in the conveyance direction. By the drive ofa conveyance motor 4 m, two rollers in each pair of rollers 4 a and 4 brotate in mutually opposite directions in a state of the paper 9 beingpinched. At this time, the paper 9 is conveyed in the conveyancedirection.

The controller 5, on the basis of a recording command that has beeninput from an external apparatus such as a PC (personal computer),controls the four heads 1 and the conveyance motors 4 m such that animage is recorded on the paper 9.

Next, a configuration of the head 1 will be described below withreference to FIG. 2 to FIG. 7. The head 1 includes a channel substrate11, an actuator unit 12, a tank 14, a protective member 15, and a COF(chip on flexible printed circuit) 18.

The channel substrate 11, as depicted in FIG. 3, includes a reservoirmember 11 a, a pressure-chamber plate 11 b, a channel plate 11 c, aprotective plate 11 d, and a nozzle plate 11 e, and these plates areadhered mutually. A plurality of pressure chambers 11 m, the pluralityof nozzles 11 n, a supply channel 11 s, and a return channel 11 r areformed in the channel substrate 11 as depicted in FIG. 2 and FIG. 3.

The pressure-chamber plate 11 b is made of a silicon monocrystallinesubstrate, and has the plurality of pressure chambers 11 m formedtherein to be cut through as depicted in FIG. 3. The plurality ofpressure chambers 11 m is arranged in rows to form two pressure-chamberrows 11 mR as depicted in FIG. 2. The plurality of pressure chambers 11m forming each pressure-chamber row 11 mR is arranged in a row at anequal distance in a direction of array (a direction orthogonal to theconveyance direction). The two pressure-chamber rows 11 mR are arrangedside-by-side in a direction orthogonal to the array direction (adirection parallel to the conveyance direction, and a facing directionin which a pair of lateral walls 11 c 1 to be described later areface-to-face). The plurality of pressure chambers 11 m is arranged inrows in a zigzag form such that respective positions thereof in thearray direction differ.

The channel plate 11 c, in a plan view, is slightly larger than thepressure-chamber plate 11 b. The channel plate 11 c is adhered to alower surface of the pressure-chamber plate 11 b. A manifold 11 s 2which is a portion of the supply channel 11 s, a channel 11 t whichconnects the manifold 11 s 2 and each pressure chamber 11 m, a descender11 p which connects each pressure chamber 11 m and each nozzle 11 n, aconnecting channel 11 u which connects the descender 11 p and the returnchannel 11 r, and the return channel 11 r are formed in the channelplate 11 c as depicted in FIG. 3. The manifold 11 s 2 and the returnchannel 11 r pass through the channel plate 11 c in a direction ofthickness thereof, and open at an upper surface and a lower surface ofthe channel plate 11 c. The manifold 11 s 2, as depicted in FIG. 2, isextended in the array direction, at both outer sides of the twopressure-chamber rows 11 mR. The return channel 11 r is extended in thearray direction, between the two pressure-chamber rows 11 mR.

A damper film 11 v which is flexible, is adhered to the lower surface ofthe channel plate 11 c to cover the manifold 11 s 2 as depicted in FIG.3. The damper film 11 v has a function of attenuating (damping) afluctuation in a pressure of ink inside the manifold 11 s 2. A spacer Sin the form of a frame is fixed to a periphery of the damper film 11 v.

The protective plate 11 d is adhered to a lower surface of the spacer Sto cover the damper film 11 v. The damper film 11 v is facing theprotective plate 11 d via a distance in between, and is protected by theprotective plate 11 d.

The plurality of nozzles 11 n communicating with the plurality ofpressure chambers 11 m respectively is formed in the nozzle plate 11 eto be cut through. The nozzle plate 11 e is adhered to the lower surfaceof the channel plate to block the return channel 11 r. The plurality ofnozzles 11 n, as depicted in FIG. 2, is arranged in two rows similarlyas the plurality of pressure chambers 11 c. The plurality of nozzles 11n is arranged in a zigzag form such that the respective positionsthereof in the array direction differ.

A reservoir 11 s 1 which is a part of the supply channel 11 s is formedin the reservoir member 11 a as depicted in FIG. 3. The reservoir 11 s1, similarly as the manifold 11 s 2, is extended in the array direction,at both outer sides of the two pressure-chamber rows 11 mR. Thereservoir 11 s 1 opens in a lower surface of the reservoir member 11 a.The reservoir member 11 a is adhered to an upper surface of the channelplate 11 c and an upper surface of the protective member 15.

Each of the supply channel 11 s and the return channel 11 r communicateswith a storage chamber 14 a of the tank 14 via a tube as depicted inFIG. 2. An ink is stored in the storage chamber 14 a. The ink in thestorage chamber 14 a inflows into the supply channel 11 s by a pump P,and is supplied to a plurality of pressure chambers 11 m in eachpressure-chamber row 11 mR from both outer sides of the twopressure-chamber rows 11 mR. Some of the ink supplied to each pressurechamber 11 m is jetted from the nozzle 11 n, and the remaining inkinflows into the return channel 11 r which is extended between the twopressure-chamber rows 11 mR, and is returned to the storage chamber 14a. Arrow marks in FIG. 2 indicate a flow of the ink that inflows fromthe pressure chamber 14 a into the return channel 11 r via the supplychannel 11 s, and then returns from the return channel 11 r to thestorage chamber 14 a.

The actuator unit 12, as depicted in FIG. 4, is arranged on an uppersurface 11 b 1 of the pressure-chamber plate 11 b. The actuator unit 12includes in order from below, a vibration plate 12 a, a common electrode12 b, a plurality of piezoelectric bodies 12 c, and a plurality ofindividual electrodes 12 d.

The vibration plate 12 a and the common electrode 12 b are formed onsubstantially whole of the upper surface 11 b 1 of the pressure-chamberplate 11 b. The vibration plate 12 a and the common electrode 12 b coverthe plurality of pressure chambers 11 m. The plurality of piezoelectricbodies 12 c and the plurality of individual electrodes 12 d are arrangedfor each pressure chamber 11 m. In other words, the plurality ofpiezoelectric bodies 12 c and the plurality of individual electrodes 12d are arranged to be facing the plurality of pressure chambers 11 mrespectively.

The vibration plate 12 a is a film of silicon dioxide formed byoxidizing a surface of the silicon monocrystalline surface of thepressure-chamber plate 11 b. The common electrode 12 b is an electrodecommon to the plurality of pressure chambers 11 m, and is arranged at aposition facing the plurality of pressure chambers 11 m between thevibration plate 12 a and the plurality of piezoelectric bodies 12 c. Theplurality of piezoelectric bodies 12 c is made of a piezoelectricmaterial such as lead zirconate titanate (PZT), and is arranged atpositions facing the plurality of pressure chambers 11 m on an uppersurface of the common electrode 12 b. The plurality of individualelectrodes 12 d is formed on upper surfaces of the plurality of thepiezoelectric bodies 12 c respectively. In other words, each individualelectrode 12 d is arranged at a position facing each pressure chamber 11m.

A portion of the piezoelectric body 12 c, sandwiched between theindividual electrode 12 d and the common electrode 12 b functions as anactuator 12 x which is deformable according to a voltage applied to theindividual electrode 12 d. In other words, the actuator unit 12 includesa plurality of the actuators 12 x covering the plurality of pressurechambers 11 m respectively. By driving the actuator 12 x facing thepressure chamber 11 m, a volume of the pressure chamber 11 m can bechanged. Thereby a pressure is applied to the ink in the pressurechamber 11 m, and the ink is jetted from the nozzle 11 n. Driving theactuator 12 x means deforming the actuator 12 x to be projected (to bebulged) toward the pressure chamber 11 m according to the voltageapplied to the individual electrode 12 d.

A protective film 12 i is provided on a portion of an upper surface ofeach individual electrode 12 d and an upper surface of the commonelectrode 12 b, where no piezoelectric body 12 has been provided, tocover a lateral surface of each piezoelectric body 12 c. The protectivefilm 12 i is for protecting the piezoelectric body 12 c, and has afunction of preventing the moisture in air from entering into thepiezoelectric body 12 c. The protective film 12 i is made of a materialsuch as aluminum oxide (alumina: Al₂O₃).

A wire 12 e is connected to each individual electrode 12 d via aconductive material B filled in a through hole cut through theprotective film 12 i (refer to FIG. 4). The plurality of wires 12 econnected to the plurality of individual electrodes 12 d respectively,as depicted in FIG. 2, is extended in a facing direction from eachindividual electrode 12 d corresponding to the two pressure-chamber rows11 mR toward an area between the two pressure-chamber rows 11 mR. Anindividual contact point 12 f is formed at a front end of each wire 12e. A plurality of the individual contact points 12 f is arranged in azigzag form along the direction of arrow, in the area between the twopressure-chamber rows 11 mR.

A pair of common contact points 12 g is provided to sandwich theplurality of individual contact points 12 f The pair of common contactpoints 12 g is electrically connected to the common electrode 12 b via aconductive material (omitted in the diagram) filled in the through holecut through the protective film 12 i.

The pair of common contact points 12 g and the plurality of individualcontact points 12 f correspond to the contact point of the presentteaching. The pair of common contact points 12 g is electricallyconnected to the common electrode 12 b of the plurality of actuators 12x. The plurality of individual contact points 12 f is electricallyconnected to the individual electrodes 12 d of the plurality ofactuators 12 x respectively.

The protective member 15, as depicted in FIG. 3, has a pair of recesses15 a, each extended in the array direction. Each recess 15 a opens in alower surface of the protective member 15. The protective member 15 isadhered to the upper surface 11 b 1 of the pressure-chamber plate 11 bvia the vibration plate 12 a, the common electrode 12 b, and theprotective film 12 i, such that the plurality of piezoelectric bodies 12c corresponding to each pressure-chamber row 11 mR is accommodated ineach recess 15 a.

The protective member 15 has a through hole 15 b at a center in thedirection orthogonal to the array direction. The reservoir member 11 ahas a through hole 11 a 1 at a center in the direction orthogonal to thearray direction. The contact points 12 f and 12 g (the individualcontact point 12 f and the common contact point 12 g) are exposedthrough the through holes 15 b and 11 a 1.

The COF 18 corresponds to the circuit board of the present teaching, andas depicted in FIG. 4, FIG. 5, and FIG. 7, includes a sheet 18 b whichhas an insulating property and which is made of polyimide, a pluralityof individual wires 18 f to be electrically connected to the pluralityof individual contact points 12 f respectively, and a pair of commonwires 18 g to be electrically connected to the pair of common contactpoints 12 g respectively. The individual wires 18 f and the common wires18 g are provided on the surface of the sheet 18 b.

One end of the COF 18 is adhered to the upper surface 11 b 1 of thepressure-chamber plate 11 b via an adhesive A, in a state of theindividual wire 18 f and the common wire 18 g facing the individualcontact point 12 f and the common contact point 12 g respectively asdepicted in FIG. 7. An ACF (anisotropic conductive film) can be used asthe adhesive A. The COF 18 includes a curved portion 18 v which is bentnear one end, and is extended upward from the curved portion 18 v, uponpassing the through holes 15 b and 11 a 1, and the other end (thereof)is electrically connected to the controller 5 (refer to FIG. 1).

The one end of the COF 18 has an adhering portion (adhering portion) 18Awhich is to be adhered to the channel substrate 11. Specifically, theadhering portion 18A is a portion (at least a portion facing the contactpoints 12 f and 12 g of the channel substrate 11) of the COF 18, facinga surface (the upper surface 11 b 1 of the pressure-chamber plate 11 b)provided with the contact points 12 f and 12 g of the channel substrate11. The adhering portion 18A of the present embodiment is a range from afront tip of the one end of the COF 18 up to the curved portion 18 v(refer to FIG. 5) in the present embodiment. The adhering portion 18Aincludes an adhering portion 18Ag of each common contact point 12 g andeach common wire 18 g, and an adhering portion 18Af of each individualcontact point 12 f and each individual wire 18 f. An area of theadhering portion 18Ag is larger than an area of the adhering portion18Af.

A driver IC 19 is mounted between the one end and the other end of theCOF 18 as depicted in FIG. 3. The driver IC 19 is electrically connectedto each of the contact points 12 f and 12 g, and the controller 5 viathe wires 18 f and 18 g. The driver IC 19 generates a drive signal fordriving the actuator 12 x on the basis of a signal from the controller5, and supplies the drive signal to each individual electrode 12 d. Anelectric potential of the common electrode 12 b is maintained to be aground electric potential.

Next, an arrangement of the return channel 11 r formed in the channelsubstrate 11 will be described specifically with reference to FIG. 5 toFIG. 7.

The pressure-chamber plate 11 b corresponds to the adhesive wall of thepresent teaching, and the return channel 11 r corresponds to the cavityof the present teaching.

The contact points 12 f and 12 g are provided to the upper surface 11 b1 of the pressure-chamber plate 11 b as depicted in FIG. 5 and FIG. 7,and the adhesive layer 18A of the COF 18 are adhered to the uppersurface 11 b 1. The return channel 11 r is provided to an opposite side(lower side) of the upper surface 11 b 1 of the pressure-chamber plate11 b.

A length of the return channel 11 r along the facing direction is theshortest in a portion of contact with the pressure-chamber plate 11 b asdepicted in FIG. 5. Specifically, a cross-section of the return channel11 r in a vertical direction (direction in which the adhering portion18A and the return channel 11 r are face-to-face) and the facingdirection has a trapezoidal shape. A length a of an upper base of thetrapezoidal shape is shorter than a length b of a lower base of thetrapezoidal shape (a<b). Here, the length a of the upper base of thetrapezoidal shape is a length along the facing direction of a portion ofthe return channel 11 r, in contact with the pressure-chamber plate 11b. The length b of the lower base of the trapezoidal shape is a lengthalong the facing direction of a portion of the return channel 11 r,farthest from the pressure-chamber plate 11 b in the vertical direction.

Let a thickness of the pressure-chamber plate 11 b bet. Let a lengthbetween the pair of side portions of the return channel 11 r of aportion the pressure-chamber plate 11 b, in contact with the returnchannel 11 r be a. In other words, let a length along the facingdirection of the portion of the return channel 11 r, in contact with thepressure-chamber plate 11 b be a. Let a pressure which is exerted to thepressure-chamber plate be x. In the present embodiment, the followingexpression is satisfied.t/a≥−1.5846x+22.75

The abovementioned expression has been derived by simulation with thepressure x=100N, 150N, and 200N, assuming a material of thepressure-chamber plate 11 b.

The channel plate 11 c includes a pair of lateral walls 11 c 1demarcating the pair of side portions of the return channel 11 rrespectively, on a side (lower side) of the pressure-chamber plate 11 b,opposite to the upper surface 11 b 1. The pair of lateral walls 11 c 1corresponds to the wall portion of the present teaching, and theadhering portion 18A is facing each of the return channel 11 r and thepair of lateral walls 11 c 1.

The channel plate 11 c further includes a plurality of narrow portions11 c 3 formed by the pair of lateral walls 11 c 1 as depicted in FIG. 2.The narrow portion 11 c 3 is a portion for which a distance between thepair of lateral walls 11 c 1 is smaller than a portion 11 c 4 adjacentto an upstream side of a direction of flow and a portion 11 c 5 adjacentto a downstream side of the direction of flow. The direction of flow isa direction in which the ink inside the return channel 11 r flows, andis a direction parallel to a direction in which the return channel 11 ris extended (in other words, the array direction). The pair of lateralwalls 11 c 1 is protruded inward at an equal interval in the directionof flow. Accordingly, the plurality of narrow portions 11 c 3 isprovided at an equal interval in the direction of flow. The adheringportion 18A is facing the narrow portion 11 c 3, to be symmetrical onthe upstream side and the downstream side of the direction of flow, withrespect to a center O of the adhering portion 18A in the direction offlow.

A plurality of columns 11 c 2 f and 11 c 2 g is provided inside thereturn channel 11 r. The columns 11 c 2 f and 11 c 2 g, as depicted inFIG. 5 and FIG. 7, connect the pressure-chamber plate 11 b and thenozzle plate 11 e, and are provided at positions facing the individualcontact point 12 f and the common contact point 12 g respectively. Thenozzle plate 11 e is facing the pressure-chamber plate 11 b sandwichingthe return channel 11 r in between, thereby blocking the return channel11 r, and corresponds to the blocking wall of the present teaching.

The columns 11 c 2 f and 11 c 2 g, as depicted in FIG. 2, are separatedapart mutually in the direction of flow, and are provided at an equalinterval in the direction of flow. The adhering portion 18A is facingthe columns 11 c 2 f and 11 c 2 g, to be symmetrical on the upstreamside and the downstream side of the direction of flow, with respect tothe center O of the adhering portion 18A in the direction of flow. Eachcolumn 11 c 2 g has a cross-sectional area orthogonal to a verticaldirection, larger than (a cross-sectional area orthogonal to thevertical direction of) each column 11 c 2 f, and a dimension of an areaof the adhering portion 18Ag facing the column 11 c 2 g is larger than adimension of an area of the adhering portion 18Af facing the column 11 c2 f.

In addition to the pair of lateral walls 11 c 1, the plurality ofcolumns 11 c 2 f and 11 c 2 g also corresponds to the wall portion ofthe present teaching, and the adhering portion 18A is facing the pair oflateral walls 11 c 1 and the columns 11 c 2 f and 11 c 2 g, to besymmetrical on the upstream and the downstream side of the direction offlow, with respect to a center O of the adhering portion 18A in thedirection of flow.

Each of the columns 11 c 2 f and 11 c 2 g, as depicted in FIG. 6, has atapered shape tapering toward the upstream side of the direction offlow. Specifically, each of the columns 11 c 2 f and 11 c 2 g isextended toward the downstream side of the direction of flow fromupstream apex portions T1 f and T1 g, and upstream apex portions T1 fand T1 g, and has a pair of upstream lateral surfaces S1 f and S1 ghaving a streamlined shape gradually approaching the pair of lateralwalls 11 c 1 respectively toward the downstream side.

Each of the columns 11 c 2 f and 11 c 2 g, furthermore, has a taperedshape tapering toward the downstream side of the direction of flow.Specifically, each of the columns 11 c 2 f and 11 c 2 g is extendedtoward the upstream side of the direction of flow from downstream apexportions T2 f and T2 g, and downstream apex portions T2 f and T2 g, andfurther has a pair of downstream lateral surfaces S2 f and S2 g having astreamlined shape gradually approaching the pair of lateral walls 11 c 1respectively toward the downstream side. The pair of downstream lateralsurfaces S2 f and S2 g is connected to the pair of upstream lateralsurfaces S1 f and S1 g respectively.

The ink inside the return channel 11 r flows as depicted by thick arrowmarks in FIG. 6, along the lateral surfaces S1 f, S1 g, S2 f, and S2 gof the columns 11 c 2 f and 11 c 2 g.

As mentioned above, according to the present embodiment, the adheringportion 18A of the COF 18 is facing not only the return channel 11 r,but also the lateral wall 11 c 1, and the columns 11 c 2 f and 11 c 2 g(refer to FIG. 2 and FIG. 5). Therefore, at the time of adhering the COF18 to the channel substrate 11, a load exerted to the adhering portion18A is supported by the lateral wall 11 c 1, and the columns 11 c 2 fand 11 c 2 g, and a problem of the pressure-chamber plate 11 b gettingdeformed due to the load is suppressed.

The adhering portion 18A is facing each lateral wall 11 c 1 in the pairof lateral walls 11 c 1. In this case, the load exerted to the adheringportion 18A being supported by the pair of lateral walls 11 c 1 fromboth sides, the problem of the pressure-chamber plate 11 b gettingdeformed is suppressed more assuredly.

A length of the return channel 11 r along the facing direction is theshortest at a portion in contact with the pressure-chamber plate 11 b(refer to FIG. 5). In this case, a portion of the pair of lateral walls11 c 1, in contact with the pressure-chamber plate 11 b supports theload exerted to the adhering portion 18A. It is possible to secure aspace inside the return channel 11 r at a portion of the pair of lateralwalls 11 c 1, away from the pressure-chamber plate 11 b.

The cross-section of the return channel 11 r in the vertical direction(direction in which the adhering portion 18A and the return channel 11 rare face-to-face) and the facing direction has a trapezoidal shape. Inthis case, it is possible to form the return channel 11 r easily.

The channel substrate 11 includes the columns 11 c 2 f and 11 c 2 g, andthe adhering portion 18A is facing the columns 11 c 2 f and 11 c 2 g(refer to FIG. 2 and FIG. 6). In this case, the load exerted to theadhering portion 18A is supported by the columns 11 c 2 f and 11 c 2 g,and the problem of the pressure-chamber plate 11 b getting deformed issuppressed more assuredly.

The adhering portion 18A is facing the plurality of columns 11 c 2 f and11 c 2 g provided to be separated apart mutually in the array direction(direction in which the return channel is extended) (refer to FIG. 2 andFIG. 6). In this case, the load exerted to the adhering portion 18A issupported by the plurality of columns 11 c 2 f and 11 c 2 g. Therefore,the problem of the pressure-chamber plate 11 b getting deformed issuppressed more assuredly. Moreover, as compared to a case of providingone large column inside the return channel 11 r, it is possible tosecure a space inside the return channel 11 r.

In the present embodiment, the cavity (return channel 11 r) forms achannel through which a liquid (ink) flows. In this case, by making anefficient use of a space facing the channel as an adhesive area of theCOF 18, a small-sizing of the head 1 is realized.

In the present embodiment, the return channel 11 r is the cavity. Thereturn channel 11 r is formed to be comparatively long (refer to FIG. 2)in order to communicate with each of the plurality of pressure chambers11 m. According to the abovementioned arrangement, it is possible to useeffectively a space facing the long channel as an adhesive area of theCOF 18.

The return channel 11 r is arranged between the two pressure-chamberrows 11 mR that are mutually adjacent, and is shared by the twopressure-chamber rows 11 mR (refer to FIG. 2 and FIG. 3). In this case,it is possible to realize simplification and small-sizing of thearrangement of the head 1, as compared to a case of providing anindividual return channel 11 r for the two pressure-chamber rows 11 mR.

The adhering portion 18A is facing the lateral wall 11 c 1, and thecolumns 11 c 2 f and 11 c 2 g, to be symmetrical on the upstream sideand the downstream side of the direction of flow, with respect to thecenter O of the adhering portion 18A in the direction of flow (refer toFIG. 2). In this case, a load is exerted symmetrically on the upstreamside and the downstream side of the direction of flow, and it ispossible to adhere the COF 18 uniformly in the direction of flow.

The adhering portion 18A is facing the columns 11 c 2 f and 11 c 2 g, tobe symmetrical on the upstream side and the downstream side of thedirection of flow, with respect to the center O of the adhering portion18A in the direction of flow (refer to FIG. 2). In this case, the loadexerted to the adhering portion 18A is supported by the columns 11 c 2 fand 11 c 2 g, symmetrically on the upstream side and the downstream sideof the direction of flow, and it is possible to adhere the COF 18uniformly in the direction of flow.

Each of the columns 11 c 2 f and 11 c 2 g has a tapered shape taperingtoward the upstream side (refer to FIG. 6). In this case, it is possibleto suppress a problem of the flow of ink being hindered by the columns11 c 2 f and 11 c 2 g.

Each of the columns 11 c 2 f and 11 c 2 g has a tapered shape taperingfurther toward the downstream side (refer to FIG. 6). In this case, itis possible to suppress a problem of air bubbles in the ink beingaccumulated.

The adhering portion 18A is facing the narrow portion 11 c 3, to besymmetrical on the upstream side and the downstream side of thedirection of flow, with respect to the center O of the adhering portion18A in the direction of flow (refer to FIG. 2). In this case, a flowvelocity (flow rate) of the ink in the narrow portion 11 c 3 increases.Accordingly, the discharge of air bubbles in the ink is facilitated.

The area of the adhering portion 18Ag adhering each common contact point12 g and each common wire 18 g is larger than the area of the adheringportion 18Af adhering each individual contact point 12 f and eachindividual wire 18 f. Moreover, an area of the adhering portion 18Agfacing the column 11 c 2 g is larger than an area of the adheringportion 18Af facing the column 11 c 2 f. In this case, by making adimension of the area facing the column 11 c 2 g, in the adheringportion 18Ag which has a comparatively larger area and which issubjected to (comparatively) heavier load, a problem of thepressure-chamber plate 11 b getting deformed is suppressed assuredly.

Let the thickness of the pressure-chamber plate 11 b be t. Let thelength between the pair of side portions of the return channel 11 r ofthe portion of pressure-chamber plate 11 b, in contact with the returnchannel 11 r be a. In other words, let the length along the facingdirection of the portion of the return channel 11 r, in contact with thepressure-chamber plate 11 b be a. Let the pressure which is exerted tothe pressure-chamber plate 11 b be x.

In the present embodiment, the following expression is satisfied.t/a≥−1.5846x+22.75

In this case, the problem of the pressure-chamber plate 11 b gettingdeformed by the pressure x is suppressed assuredly.

Second Embodiment

Next, a head 201 according to a second embodiment of the presentteaching will be described below with reference to FIG. 8.

While in the first embodiment, the cross-sectional shape of the returnchannel 11 r is a trapezoidal shape as depicted in FIG. 5, in thepresent embodiment, a cross-sectional shape of a return channel 211 r isa projected shape (projection shape) as depicted in FIG. 8.Specifically, the return channel 211 r includes a small rectangularportion 211 r 1 and a large rectangular portion 211 r 2 which is largerthan the small rectangular portion 211 r 1, both having a cross-sectionalong a vertical direction (a direction in which the adhering portion18A and the return channel 211 r are face-to-face), and the facingdirection.

According to the present embodiment, by letting the cross-section of thereturn channel 211 r to be the projected shape (projection shape), it ispossible to form the return channel 211 r easily by using two members(refer to two plates 211 cx and 211 cy of a channel plate 211 c).Specifically, the channel plate 211 c includes the plate 211 cx whichdemarcates the small rectangular portion 211 r 1 and the plate 211 cywhich demarcates the large rectangular portion 211 r 2. The plate 211 cxis adhered to the lower surface of the pressure-chamber plate 11 b, theplate 211 cy is adhered to a lower surface of the plate 211 cx, and thenozzle plate 11 e is adhered to a lower surface of the plate 211 cy.Apart from the large rectangular portion 211 r 2, a connecting channel211 u which connects the descender 11 p (refer to FIG. 3) and the returnchannel 211 r, is formed in the plate 211 cy. The manifold 11 s 2, thechannel 11 t, and the descender 11 p are formed in the two plates 211 cxand 211 cy.

A length of the return channel 211 r along the facing direction, similarto that of the return channel 11 r in the first embodiment, is theshortest in a portion of contact with the pressure-chamber plate 11 b.Specifically, a length a2 along the facing direction of the smallrectangular portion 211 r 1 is shorter than a length b2 along the facingdirection of the larger rectangular portion 211 r 2 (a2<b2).Accordingly, similarly as in the first embodiment, it is possible tosupport the load exerted to the adhering portion 18A at a portion of apair of lateral walls 211 c 1, in contact with the pressure-chamberplate 11 b, and to secure a space inside the return channel 11 r at aportion of the pair of lateral walls 211 c 1, away from thepressure-chamber plate 11 b.

Third Embodiment

Next, a head 301 according to a third embodiment of the present teachingwill be described below with reference to FIG. 9.

In the first embodiment, the cross-sectional shape of the return channel11 r is a trapezoidal shape as depicted in FIG. 5. In the presentembodiment, a cross-sectional shape of a return channel 311 r is ahexagonal shape as depicted in FIG. 9. Specifically, the return channel311 r has a hexagonal-shaped cross section along a vertical direction (adirection in which the adhering portion 18A and the return channel 311 rare face-to-face) and the facing direction.

According to the present embodiment, the cross-section of the returnchannel 311 r is let to be hexagonal-shaped. Consequently, it ispossible to form the return channel 311 r easily by using two members(refer to two plates 311 cx and 311 cy of a channel plate 311 c).Specifically, the channel plate 311 c includes the plate 311 cx whichdemarcates an upper-half space (trapezoidal in cross-sectional view) ofthe return channel 311 r and the plate 311 cy which demarcates alower-half space (reverse trapezoidal in cross-sectional view) of thereturn channel 311 r. The plate 311 cx is adhered to the lower surfaceof the pressure-chamber plate 11 b, the plate 311 cy is adhered to alower surface of the plate 311 cx, and the nozzle plate 11 e is adheredto a lower surface of the plate 311 cy. Apart from the upper-half spaceof the return channel 311 r, a connecting channel 311 u which connectsthe descender 11 p (refer to FIG. 3) and the return channel 311 r isformed in the plate 311 cy. The manifold 11 s 2, the channel 11 t, andthe descender 11 p are formed in the two plates 311 cx and 311 cy.

A length of the return channel 311 r along the facing direction, similarto that of the return channel 11 r in the first embodiment, is theshortest in a portion of contact with the pressure-chamber plate 11 b.Accordingly, similarly as in the first embodiment, a portion of a pairof lateral walls 311 c 1 in contact with the pressure-chamber plate 11b, supports the load exerted to the adhering portion 18A. It is possibleto secure a space inside the return channel 311 r at a portion of thepair of lateral walls 311 c 1, away from the pressure-chamber plate 11b.

Let a length along the facing direction of a portion of the returnchannel 311 r, in contact with pressure-chamber plate 11 b be a3. Let alength along the facing direction of a portion of the return channel 311r, farthest in the vertical direction from the pressure-chamber 11 b beb3. Let a length along the facing direction of a portion of the returnchannel 311 r other than the portion in contact with thepressure-chamber 11 b and the portion farthest in the vertical directionfrom the pressure-chamber plate 11 b be c3. In this case, the length a3and the length b3 are shorter than the length c3 (c3>a3=b3). In a casein which, an ink containing a sedimentation component (such as pigment)flows through the return channel 311 r, when a length along the facingdirection of the portion of the return channel 311 r, farthest from thepressure-chamber plate 11 b is longer than the length along the facingdirection of the other portion, a corner portion is formed at an end inthe facing direction of the portion of the return channel 311 r,farthest from the pressure-chamber plate 11 b (refer to a corner portion11 ra in FIG. 5), and a problem of accumulation of the sedimentationcomponent in the corner portion arises. Regarding this point, accordingto the present embodiment, it is possible to suppress the abovementionedproblem by the corner portion not being formed.

Fourth Embodiment

Next, a head 401 according to a fourth embodiment of the presentteaching will be described below with reference to FIG. 10.

In the third embodiment, the cross-sectional shape of the return channel311 r is the hexagonal shape as depicted in FIG. 9. In the presentembodiment, a cross-sectional shape of a return channel 411 r is anelliptical shape as depicted in FIG. 10. Specifically, the returnchannel 411 r has an elliptical-shaped cross section along a verticaldirection (a direction in which the adhering portion 18A and the returnchannel 411 r are face-to-face) and the facing direction.

A channel 411 c includes a plate 411 cx which demarcates an upper-halfspace of the return channel 411 r, and a plate 411 cy which demarcates alower-half space of the return channel 411 r, similarly as in the thirdembodiment. The plate 411 cx is adhered to the lower surface of thepressure-chamber plate 11 b, the plate 411 cy is adhered to a lowersurface of the plate 411 cx, and the nozzle plate 11 e is adhered to alower surface of the plate 411 cy. Apart from the lower-half space ofthe return channel 411 r, a connecting channel 411 u which connects thedescender 11 p (refer to FIG. 3) and the return channel 411 r is formedin the plate 411 cy. The manifold 11 s 2, the channel 11 t, and thedescender 11 p are formed in the two plates 411 cx and 411 cy.

Similar to the return channel 311 r in the third embodiment, a length ofthe return channel 411 r along the facing direction is the shortest in aportion of contact with the pressure-chamber plate 11 b. Accordingly,similarly as in the first embodiment and the third embodiment, a portionof the return channel 411 r in contact with the pressure-chamber plate11 b of a pair of lateral walls 411 c 1 supports a load exerted to theadhering portion 18A. It is possible to secure a space inside a portionof the return channel 411 r away from the pressure-chamber plate 11 b ofthe pair of lateral walls 411 c 1.

Let a length along the facing direction of a portion of the returnchannel 411 r, in contact with the pressure-chamber plate 11 b be a4.Let a length along the facing direction of a portion of the returnchannel 411 r, farthest in the vertical direction from thepressure-chamber plate 11 b be b4. Let a length along the facingdirection of a portion of the return channel 411 r other than theportion in contact with the pressure-chamber plate 11 b and the portionfarthest in the vertical direction from the pressure-chamber plate 11 bbe c4. For example, let a length in the facing direction at a center inthe vertical direction of the return channel 411 r be c4. For the returnchannel 411 r, a relationship c4>a4=b4 is established similarly as forthe return channel 311 r in the third embodiment. Consequently,according to the present embodiment, in a case in which, an inkcontaining a sedimentation component (such as pigment) flows through thereturn channel 411 r, a corner portion (refer to the corner portion 11ra in FIG. 5) is not formed, and it is possible to suppress the problemof accumulation of the sedimentation component in the corner.

Fifth Embodiment

Next, a head 501 according to a fifth embodiment of the present teachingwill be described below with reference to FIG. 11.

In the first embodiment, the return channel 11 r has a substantiallyuniform width except for the narrow portion 11 c 3 as depicted in FIG.2. However, in the present embodiment, a width (a length in the facingdirection) of a return channel 511 r becomes smaller from the upstreamside toward the downstream side of the direction of flow as depicted inFIG. 11. According to the present embodiment, the width of the returnchannel 511 r narrows gradually from the upstream side toward thedownstream side in the direction of flow. Accordingly, it is possible toform easily an area facing a pair of lateral walls 511 c 1, in theadhering portion 18A. Moreover, by the flow velocity of ink increasingfrom the upstream side toward the downstream side in the direction offlow, the discharge of air bubbles in the ink is facilitated.

In the present embodiment, the narrow portion 11 c 3, and the columns 11c 2 f and 11 c 2 g are omitted.

Sixth Embodiment

Next, a head 601 according to a sixth embodiment of the present teachingwill be described below with reference to FIG. 12.

In the first embodiment, the return channel 11 r is linear (straight)along the direction of flow (direction in which the return channel 11 ris extended) when viewed from the vertical direction as depicted in FIG.2. In the present embodiment, a return channel 611 r has a zigzag shapealong the direction of flow (direction in which the return channel 611 ris extended) when viewed from the vertical direction as depicted in FIG.12. According to the present embodiment, by the return channel 611 rhaving the zigzag shape, it is possible to form easily an area facing apair of wall portions 611 c 1, in the adhering portion 18A. Moreover, ina case in which the ink containing a sedimentation component (such aspigment) flows inside the return channel 611 r, it is possible tosuppress the problem of accumulation of the sedimentation componentinside the return channel 611 r.

In the present embodiment, the narrow portion 11 c 3, and the columns 11c 2 f and 11 c 2 g are omitted.

The preferred embodiments of the present teaching have been describedabove. However, the present teaching is not restricted to theabovementioned embodiments, and various design modifications arepossible without departing from the scope of the patent claims (presentteaching).

Modified Embodiment

The adhering portion may be facing one of the pair of wall portions, andmay not be facing the other of the pair of wall portions. The adheringportion may be facing the wall portion asymmetrically on the upstreamside and the downstream side of the direction of flow, with respect tothe center of the adhering portion in the direction of flow. Theadhering portion may not be limited to be facing the plurality ofcolumns, and may be facing one column.

The column is not restricted to have the tapered shape, and may becircular cylindrical shaped. One column may be provided inside thecavity, or the column may not be provided inside the cavity.

The length along the facing direction of the portion of the returnchannel (cavity) of the third embodiment and the fourth embodiment, incontact with the adhesive wall, and the length in the facing directionof the portion of the return channel (cavity) of the third embodimentand the fourth embodiment farthest from the adhesive wall are mutuallysame. However, these lengths may differ provided that these lengths areshorter than the length along the facing direction of the portion otherthan the portion in contact with the adhesive wall and the portionfarthest from the adhesive wall. The length along the facing directionof the cavity is not restricted to be the shortest in the portion incontact with the adhesive wall, and the length along the facingdirection may be uniform. The cross-sectional shape of the cavity is notrestricted to be the trapezoidal shape, the projected shape (projectionshape), the hexagonal shape, and the elliptical shape, and may be ashape such as a rectangular shape and a circular shape. The cavity isnot restricted to the return channel, and may be a supply channel (achannel that supplies a liquid to the plurality of pressure chambers).The cavity may not include a channel through which a liquid flows (inother words, a liquid may not flow through the cavity). The blockingwall which blocks the cavity may not be there (in other words, thecavity may be in the form of a recess opening in a direction away fromthe adhesive wall).

The number of pressure-chamber rows may not be restricted to two, andmay be one, or three or more than three. Moreover, the pressure chambersmay not be arranged to form a pressure-chamber row.

The return channel may be arranged between the two pressure chambers.The return channel may not be formed in the channel substrate (in otherwords, an arrangement is not restricted to an arrangement in which theink is circulated between the storage chamber and the pressure chamber).The channel substrate is not restricted to include the plurality ofmembers that are adhered mutually, and may include a single member.

The actuator is not restricted to be of a piezo type in which apiezoelectric element as in the abovementioned embodiment has been used,and may be of some other type (such as a thermal type in which a heaterelement is used, and of an electrostatic type in which an electrostaticforce is used).

The liquid discharge head is not restricted to be of a line type, andmay be of a serial type (such as a type in which a liquid is jetted onto a recording medium that is conveyed along a conveyance direction,while making the head scan along a direction orthogonal to theconveyance direction). Moreover, the liquid discharge apparatus is notrestricted to be equipped with a head unit which includes a plurality ofliquid discharge heads, and may include a single liquid discharge head.The liquid to be jetted by the liquid discharge head is not restrictedto ink, and it may be an arbitrary liquid (such as a treatment liquidwhich makes a component in the ink coagulate or precipitate. Therecording medium is not restricted to a paper, and may be an arbitrarymedium (such as a cloth) on which the recording is possible. The presentteaching is not restricted to the printer, and is also applicable to afacsimile, a copy machine, and a multifunction device.

What is claimed is:
 1. A liquid discharge head, comprising: a channelsubstrate including a nozzle, a pressure chamber communicating with thenozzle, an actuator covering the pressure chamber, and a contact pointelectrically connected to the actuator; and wherein the channelsubstrate includes: a plate having a surface on which the contact pointis located, wherein the surface includes an adhering portion configuredto adhere to a circuit board including a wire electrically connected tothe contact point, and walls defining a hollow space located on a sideopposite to the surface of the plate, and the adhering portion overlapswith both the hollow space and a portion of the walls in an orthogonaldirection orthogonal to the surface of the plate.
 2. The liquiddischarge head according to claim 1, wherein the walls of the channelsubstrate includes a pair of lateral walls defining a pair of lateralportions of the hollow space, respectively, and the adhering portionoverlaps with each of the pair of lateral walls in the orthogonaldirection.
 3. The liquid discharge head according to claim 2, wherein alength of the hollow space along a facing direction in which the lateralwalls face each other is the shortest in an overlapping portion, of thehollow space, overlapping with the adhering portion in the orthogonaldirection.
 4. The liquid discharge head according to claim 3, wherein across-section, of the hollow space, along a plane including the facingdirection and the orthogonal direction has a trapezoidal shape.
 5. Theliquid discharge head according to claim 3, wherein a cross-section, ofthe hollow space, along a plane including the facing direction and theorthogonal direction has a convex shape including a small rectangularportion and a large rectangular portion which is larger than the smallrectangular portion.
 6. The liquid discharge head according to claim 3,wherein a length of the facing portion of the hollow space along thefacing direction, and a length of a distant portion, of the hollowspace, farthest from the plate along the facing direction are shorterthan a length of a portion of the hollow space along the facingdirection other than the facing portion and the distant portion.
 7. Theliquid discharge head according to claim 6, wherein a cross-section ofthe hollow space along a plane including the facing direction and theorthogonal direction, has a hexagonal shape.
 8. The liquid dischargehead according to claim 1, wherein the channel substrate furtherincludes, a blocking wall overlapping with the plate in the orthogonaldirection, sandwiching the hollow space between the plate and theblocking wall in the orthogonal direction, and blocking the hollowspace, and a column being located in the hollow space, connecting theplate and the blocking wall, and being a part of the walls, and theadhering portion overlaps with the column in the orthogonal direction.9. The liquid discharge head according to claim 8, wherein the channelsubstrate further includes another column, and the column and theanother column are mutually separated in an extending direction in whichthe hollow space is extended, and the adhering portion overlaps withboth the column and the another column.
 10. The liquid discharge headaccording to claim 1, wherein the hollow space forms a channel throughwhich a liquid flows.
 11. The liquid discharge head according to claim10, wherein the channel substrate includes a return channel configuredto return a liquid from each of the plurality of pressure chambers to astorage chamber configured to store the liquid, and the return channelis the hollow space.
 12. The liquid discharge head according to claim11, wherein the plurality of pressure chambers is arranged in rows toform a plurality of pressure-chamber rows, and the hollow space isarranged between two adjacent pressure-chamber rows out of the pluralityof pressure-chambers rows, and is shared by the two adjacentpressure-chamber rows.
 13. The liquid discharge head according to claim10, wherein the adhering portion overlaps with the walls in theorthogonal direction so that the adhering portion becomes symmetrical onan upstream and a downstream in a flow direction of a liquid flowingthrough the hollow space in the adhering portion, with respect to acenter of the flow direction.
 14. The liquid discharge head according toclaim 13, wherein the channel substrate further includes, a blockingwall overlapping with the plate in the orthogonal direction, sandwichingthe hollow space between the plate and the blocking wall in theorthogonal direction, and blocking the hollow space, and a column beinglocated in the hollow space, connecting the plate and the blocking wall,and being a part of the walls, and the adhering portion overlaps withthe column in the orthogonal direction so that the adhering portionbecomes symmetrical on an upstream and a downstream in the flowdirection, with respect to the center of the flow direction.
 15. Theliquid discharge head according to claim 14, wherein the column has atapered shape which is tapered toward the upstream in the flowdirection.
 16. The liquid discharge head according to claim 15, whereinthe column has a tapered shape which is tapered toward the downstream inthe flow direction.
 17. The liquid discharge head according to claim 13,wherein the channel substrate further includes a narrow portion definedby a pair of lateral walls defining a pair of lateral portions of thehollow space, respectively, a width of the narrow portion along a facingdirection in which the lateral walls face each other being smaller thana width of adjacent portions along the facing direction, the adjacentportions being located on the upstream and the downstream of the narrowportion in the flow direction, and the adhering portion overlaps withthe narrow portion in the orthogonal direction, to be symmetrical on theupstream side and the downstream side of the direction of flow, withrespect to a center of the direction of flow in the adhering portion.18. The liquid discharge head according to claim 10, wherein the hollowspace has a shape in which a width in the orthogonal direction and aflow direction of a liquid flowing in the hollow space becomes smallerfrom the upstream to the downstream in the flow direction.
 19. Theliquid discharge head according to claim 1, wherein the hollow space hasa zigzag shape along an extending direction in which the hollow space isextended.
 20. The liquid discharge head according to claim 1, whereinthe channel substrate further includes: another nozzle, and anotherpressure chamber communicating with the another nozzle, and the liquiddischarge head further includes another actuator the actuator coveringthe another pressure chamber, and the contact point of the channelsubstrate includes a common contact point electrically connected to boththe actuator and the another actuator, and a plurality of individualcontact points electrically connected to both the actuator and theanother actuator, and the wires include a common wire electricallyconnected to the common contact point, and a plurality of individualwires electrically connected to the plurality of individual contactpoints respectively.
 21. The liquid discharge head according to claim20, wherein an area of the adhering portion in which the common contactpoint and the adhering portion are adhered is larger than an area of theadhering portion in which plurality of individual contact points and theplurality of individual wires respectively, and a dimension of an areaoverlapping with the walls in the orthogonal direction is large.
 22. Theliquid discharge head according to claim 1, wherein the walls of thechannel substrate includes a pair of lateral walls defining a pair oflateral portions of the hollow space, wherein a thickness “t” of theplate in the orthogonal direction, a length “a” between the pair oflateral portions of the hollow space at which the plate overlaps withthe hollow space, and a pressure “x” being exerted to the plate satisfythe following expressiont/a≥−1.5846x+22.75.